1. Field of the Invention
The present invention generally relates to the implementation of split charging (SPC) in an Internet protocol multimedia subsystem (IMS), and in particular, to methods and apparatuses for implementation of SPC in an IMS, allowing IMS users to negotiate at setup and at a modification of a session initiation protocol (SIP) session which user will be charged for each multimedia component of the session.
2. Description of the Related Art
The 3rd Generation Partnership Protocol (3GPP) Stage 1 defines general requirements for charging in its technical services, TS 22.115 and TS 22.101. Specifically, TS 22.115 defines general requirements for applying charges flexibly to either the calling party or the called party, charging a third party for the session, allowing the splitting of charges among the calling party, the called party, and the third party, and charging according to the type of services and media used. Chapter 16 of TS 22.101 defines general requirements for alternate party charging. The general requirements include a provision for the chargeable party to be changed during the life of the call, and a provision stating that a user is charged for a call only after the user's consent to accepting the call is obtained. The user's consent may be obtained dynamically or through the user's service profile.
The European Telecommunications Standards Institute (ETSI) also defines general requirements for charging in their Telecons & Internet conveyed Services & Protocols for Advanced Networks (TISPAN) TS 181002, version 1.1.1, chapter 8.4.4, providing a requirement for support of reverse charging (REV) in the Next Generation Network (NGN).
The ITU Telecommunication Standardization Sector (ITU-T), which coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU), standardized REV as an integrated services digital network (ISDN) supplementary service, as outlined in ITU-T standards, I.256.3 (stage 1), Q.86.3 (stage 2), Q.736.3, and Q.956.3 (stage 3, network and user signaling).
Four cases are defined in the aforementioned ITU-T standards.
The first case defines REV requested by a calling user at a call set-up time. In this first case, the service requested needs to be accepted by the called user.
The second case defines REV for the rest of the call, whereby the REV is requested by the calling user or the called user during the active phase of the call.
The third case defines REV for the entire call, whereby the REV is requested by the called user during the active phase of the call.
The fourth case defines an unconditional REV, which includes a subscription-based service for the called user.
The calling user must indicate his request for REV in the first and second cases, but not in the fourth case. In the first and second (where the REV request is initiated by the calling party) cases, the called user is presented with the REV request and active acceptance to the REV request is required. In the third and fourth cases, the called user is only informed about the request, which is automatically accepted; therefore, no acceptance of the requested REV is needed from the called user.
If the required service REV request acceptance is missing, the call will be cleared in the first and fourth cases, whereas the call with unaccepted REV request will continue unchanged in the second and third cases.
For a specific call, REV may only be invoked once. After a successful service invocation, any further request results in the call being cleared in the first and fourth cases, and the call with REV request continues unchanged in the second and third cases. However, an unsuccessful service invocation may be followed by a successful service invocation, even in the same case.
Further, service interworking has been defined for other ISDN supplementary services (SS), e.g. for call forwarding (CFW) services.
Therefore, as evidenced by REV being included in the 3GPP Stage 1, a clear business need has arisen for dynamic/static service options allowing IMS users to negotiate about and agree upon SPC for services in an IMS. Accordingly, what is needed is a method and apparatus for implementation of SPC in an IMS which allows IMS users to negotiate at setting up/during a SIP session which user will be charged for each multimedia component of the session.